Copyright (c) 2016-present, RxJava Contributors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
the License for the specific language governing permissions and limitations under the License.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.internal.operators.single;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;

Breaks the references between the upstream and downstream when the Maybe terminates.
History: 2.1.5 - experimental
Type parameters:
<T> – the value type
Since:
2.2/**
 * Breaks the references between the upstream and downstream when the Maybe terminates.
 * <p>History: 2.1.5 - experimental
 * @param <T> the value type
 * @since 2.2
 */
public final class SingleDetach<T> extends Single<T> {

    final SingleSource<T> source;

    public SingleDetach(SingleSource<T> source) {
        this.source = source;
    }

    @Override
    protected void subscribeActual(SingleObserver<? super T> observer) {
        source.subscribe(new DetachSingleObserver<T>(observer));
    }

    static final class DetachSingleObserver<T> implements SingleObserver<T>, Disposable {

        SingleObserver<? super T> downstream;

        Disposable upstream;

        DetachSingleObserver(SingleObserver<? super T> downstream) {
            this.downstream = downstream;
        }

        @Override
        public void dispose() {
            downstream = null;
            upstream.dispose();
            upstream = DisposableHelper.DISPOSED;
        }

        @Override
        public boolean isDisposed() {
            return upstream.isDisposed();
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            upstream = DisposableHelper.DISPOSED;
            SingleObserver<? super T> a = downstream;
            if (a != null) {
                downstream = null;
                a.onSuccess(value);
            }
        }

        @Override
        public void onError(Throwable e) {
            upstream = DisposableHelper.DISPOSED;
            SingleObserver<? super T> a = downstream;
            if (a != null) {
                downstream = null;
                a.onError(e);
            }
        }
    }
}